Spinneret with stream guide

ABSTRACT

A stream guide finger is mounted coaxially within a spinneret capillary and extends downwardly beyond the capillary discharge opening, reducing the tendency of the molten stream to flick, bend or drip.

United States Patent [72] Inventor John M. Green Gulf Breeze, Fla. [21 Appl. No. 797,933 Y [22] Filed Feb. 10, 1969 [45] Patented Sept. 21,1971 [73] Assignee Monsanto Company St. Louis, Mo.

[ 54] SPINNERET WITH STREAM GUIDE 6 Claims, 3 Drawing Figs.

[52] U.S. Cl 264/176, 264/177, 18/8 [51] Int. Cl 1328b 21/54, B291 3/00, D01d 3/00 [50] Field of Search 264/ 1 77, 176; 18/8 SC References Cited UNITED STATES PATENTS Bundy Grafried l-leynen et a1.. Heynen et a1 Dietzsch et al. Burke et a1. Atfreld et al... Howes et a1.

Primary Examiner-Jay H. Woo

Almmoyx- Kelly 0. Corley and Stanley M. Tarter 28/82 18/8 SC 18/8 SC 18/8 SC 18/8 SC 18/8 SC 18/8 SC ABSTRACT: A stream guide finger is mounted cozixiully within a spinneret capillary and extends downwardly beyond the capillary discharge opening, reducing the tendency of the molten stream to flick, bend or drip.

PATENTEI] s02] ism 3,608,040

' INVENTOR. JOHN MANNING GREEN ATTORNEY SPINNERET WITH STREAM GUIDE The invention relates to a spinneret construction for melt spinning continuous filaments, wherein the polymer stream has a reduced tendency to divert from its normal and desired flow path.

In conventional melt spinning, molten polymer is extruded downwardly through a spinneret capillary or orifice, the molten stream then being cooled and solidified into a solid filament before being wound as a continuous filament. A significant cost factor in this process is the tendency of the molten polymer to increasingly divert from a steady stream at the exit of the orifice, and to perform improperly thereafter. Thus the molten stream immediately below the orifice exit may erratically flick abruptly to the side, or may gradually bend farther and farther to one side. In either case, the molten stream may eventually be deformed far enough to touch the spinneret face. This disrupts the molten stream, and the polymer thereafter drips from that orifice. These problems have formerly been corrected by periodically wiping the lower face of the spinneret with a brass blade or the like, in combination with coating the spinneret face with a material such as silicone. This prior art solution to the problem interrupts production and eventually damages the spinning orifices.

It has been discovered that the occurrence of flicking, bending and dripping can be substantially reduced by extending a guide finger along the axis of the spinneret orifice, the lower free end of the finger projecting beyond the orifice exit by a distance equal to at least one-half the largest orifice dimension at the exit. 1

Accordingly, the primary object of the invention is to provide a novel method and apparatus for melt spinning.

A further object is to provide a method and apparatus of the above character permitting increased production from a melt spinning unit.

A further object is to provide a method and apparatus of the above character which reduces the occurrence of flicking, bending and dripping.

Other objects will in part appear hereinafter, and will in part be obvious from the following detailed disclosure taken in connection with the accompanying drawing, wherein:

FIG. I is a simplified front elevation view of an exemplary melt spinning unit according to the invention;

FIG. 2 is a top plan view of a fragment of the FIG. 1 spinneret plate, showing the stream guide member positioned in the counterbore; and

FIG. 3 is a vertical sectional view taken along line 3-3 in FIG. 2, showing the preferred construction of the stream guide member.

As illustrated in FIG. 1, the invention is applicable to melt spinning of continuous filaments. As shown therein, metering pump 20 mounted on spinneret block 22 extrudes molten polymer through spinneret orifices in spinneret plate 24. The several molten streams 26 issuing from the spinneret orifices flow downwardly in continuous streams past an outlet 28 for transversely flowing quenching air. As illustrated, outlet 28 can be in the form of a generally vertical screen, the air being supplied through the screen at a relatively low velocity to avoid disrupting the molten streams. Typical air velocities are less than 20 feet per second.

The molten streams 26 become solidified at some point between spinneret plate 24 and convergence guide 30, where they are gathered together or converged into a continuous filament thread-line 32. Thread-line 32 conventionally has a suitable spin finish applied thereto by finish wheel 34. Threadline 32 next proceeds over feed roll 36 and its associated separator roll 38, prior to being wound on package 40 by conventional apparatus (not shown).

Construction of the spinnerets is shown in FIGS. 2 and 3. Counterbore 42 extends downwardly from upper surface 44 of spinneret plate 24, terminating in a frustoconical bottom wall 46. Spinning orifice or capillary 48 extends downwardly from and coaxially with the counterbore to its exit or discharge end at the lower surface 50 of plate 24. The apparatus as thus far specifically described is conventional.

According to the invention, a stream guide member includes a body portion 52 positioned in counterbore 42 and resting on surface 46. Guide finger 54, integral with body portion 52, extends downwardly through capillary 48 along the capillary axis. Body portion 52 is relieved in regions adjacent the lateral wall of counterbore 42 and surface 46, to permit polymer to flow past body portion 52 to the annular flow passage defined by finger 54 and the lateral wall of capillary 48. Finger 54 is solid, as opposed to hollow or capillary tubes used for injecting air in the spinning of hollow filaments, such as are disclosed in U.S. Pat. Nos. 3,081,490 and 3,121,254. Finger 54 tapers in cross section below the plane of surface 50 and terminates in a lower free end or tip 56 at a point well below the plane of surface 50.

It is essential that the vertical distance between tip 56 and the plane of surface 50 be properly related to the greatest dimension of capillary 58 in the plane of surface 50. The ratio of these respective dimensions is referred to hereafter as the extension ratio. For example, if tip 56 projects below surface 50 a distance equal to the radius of capillary 48, the extension ratio would be one-half. The extension ratio according to the invention must be at least one-half, and is preferably less than five. The optimum range is between one and three. Thus, for a right circularly cylindrical capillary having a given radius, tip 56 may be between one and 10 radii below surface 50, and preferably between one and three diameters below surface 50. When the extension ratio is less than about one-half, the finger does not project sufficiently far to adequately stabilize the molten stream against bending and flicking. When the extension ratio exceeds about five, the finger produces excessive frictional drag on the viscous polymer, tending to disrupt the molten stream.

The molten polymer emerging from capillary 48 is subjected to low velocity air at a pressure substantially equal to normal atmospheric pressure. The present invention is therefore readily distinguishable from prior art disclosures such as U.S. Pat. No. 3,017,664 to Ladisch, both in the dimensions of the guide finger and in the process conditions. The products produced by such prior art disclosures are likewise entirely different, being staple fibers as opposed to the continuous filaments produced by the present invention.

What I claim is:

1. A spinneret plate having a plurality of fluid passages extending therethrough, each passage comprising:

A. an extrusion orifice extending through said plate from a pressure side to a discharge side thereof; and

B. a solid guide finger extending through said orifice and terminating in a free end, said free end extending farther from the discharge side of said plate than one-half the largest dimension of said orifice perpendicular to the axis of said orifice at the discharge end of said orifice.

2. The apparatus defined in claim 1 wherein said orifice is right circularly cylindrical, and wherein said largest dimension is a diameter of the right circular cylinder defining said orifice.

3. The apparatus defined in claim 1, wherein said free end extends farther than two times said largest dimension.

4. The apparatus defined in claim 1 wherein the upper end of said orifice communicates with a counterbore.

5. The apparatus defined in claim 1, wherein said finger has a smaller cross section at said free end than at said orifice.

6. A method of melt spinning a melt-spinnable molten fiberforming polymer, comprising,

A. extruding said molten polymer along an annular path between a spinneret orifice wall and a stream guide finger within and extending beyond the discharge end of said orifice;

B. flowing said molten polymer along said guiding finger past the discharge end of said orifice;

C. controlling gas flow in the vicinity of said finger to a velocity less than 20 ft. per second whereby said polymer flows from the end of said finger in a continuous stream devoid of a central cavity;

D. cooling said continuous stream to a temperature below the melt point of said polymer, thereby forming a continuous solid filament; and

E. collecting said continuous filament in an orderly fashion. 

2. The apparatus defined in claim 1 wherein said orifice is right circularly cylindrical, and wherein said largest dimension is a diameter of the right circular cylinder defining said orifice.
 3. The apparatus defined in claim 1, wherein said free end extends farther than two times said largest dimension.
 4. The apparatus defined in claim 1 wherein the upper end of said orifice communicates with a counterbore.
 5. The apparatus defined in claim 1, wherein said finger has a smaller cross section at said free end than at said orifice.
 6. A method of melt spinning a melt-spinnable molten fiber-forming polymer, comprising, A. extruding said molten polymer along an annular path between a spinneret orifice wall and a stream guide finger within and extending beyond the discharge end of said orifice; B. flowing said molten polymer along said guiding finger past the discharge end of said orifice; C. controlling gas flow in the vicinity of said finger to a velocity less than 20 ft. per second whereby said polymer flows from the end of said finger in a continuous stream devoid of a central cavity; D. cooling said continuous stream to a temperature below the melt point of said polymer, thereby forming a continuous solid filament; and E. collecting said continuous filament in an orderly fashion. 